Vehicular checkpoints are a familiar and widely used method for securing national borders around the world. In the United States, vehicular inspections at border checkpoints are typically executed in three phases: pre-inspection, primary inspection and optional secondary inspection. In the pre-inspection phase, canine units perform a random inspection in traffic lanes on waiting vehicles to detect indications of smuggling. Other techniques, such as video surveillance and radiation monitoring, etc., may also be employed.
Suspicious vehicles are flagged for additional scrutiny during the primary inspection phase. During this phase, a vehicle driver may be briefly questioned and documentation checked. The driver may also be evaluated for indications that a secondary inspection is warranted. These interviews usually last only 10-15 seconds per vehicle, but can back traffic up for miles, causing border delays of hours.
In the optional secondary inspection phase, the driver and vehicle undergo closer scrutiny, which may take 20-30 minutes, or even longer in some cases. As inspection resources are limited, the goal of the inspection process is to maximize the productivity and safety of the secondary search phase. It will be appreciated that a low false alarm rate to trigger the secondary search phase is desirable.
A variety of well-known systems are used at checkpoints and border crossings. For example, X-ray backscatter systems can be used to inspect trucks at border crossings. However, these systems are slow, are range-limited, employ ionizing radiation, and are expensive. Further, as “backscatter” is really reflected radiation, any detected items will obscure or mask items behind them. Geophones, stethoscopes, and other hand-held detection devices are also used, but require intimate contact with the vehicle or container. As these inspection techniques are time-intensive, they are typically used on only a sampling of containers, as well as for vehicles selected for secondary inspections.
Canine inspections can be effective, but require close proximity of dogs to vehicles and may take significant time. Canines also require handlers to provide these dogs with constant care and supervision. In addition, these dogs require periodic re-certification, and they become less effective over time. Further, a canine's effective endurance can be as little as fifteen minutes in inclement weather.